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Sunday, 11 October 2015

Herniated nucleus pulposus is prolapse of an
intervertebral disk through a tear in the surrounding annulus fibrosus. The
tear causes pain; when the disk impinges on an adjacent nerve root, a segmental
radiculopathy with paresthesias and weakness in the distribution of the
affected root results. Diagnosis is usually by MRI or CT. Treatment of mild
cases is with analgesics as needed. Bed rest is rarely indicated. Patients with
progressive or severe neurologic deficits, intractable pain, or sphincter
dysfunction may require immediate or elective surgery (eg, diskectomy,
laminectomy).

Spinal vertebrae are separated by cartilaginous disks
consisting of an outer annulus fibrosus and an inner nucleus pulposus. When
degenerative changes (with or without trauma) result in protrusion or rupture
of the nucleus through the annulus fibrosus in the lumbosacral or cervical
area, the nucleus is displaced posterolaterally or posteriorly into the
extradural space. Radiculopathy occurs when the herniated nucleus compresses or
irritates the nerve root. Posterior protrusion may compress the cord or cauda
equina, especially in a congenitally narrow spinal canal (spinal stenosis). In
the lumbar area, > 80% of disk ruptures affect L5 or S1 nerve
roots; in the cervical area, C6 and C7 are most commonly affected. Herniated
disks are common.

Symptoms and Signs

Herniated disks often cause no symptoms,
or they may cause symptoms and signs in the distribution of affected nerve
roots. Pain usually develops suddenly, and back pain is typically relieved by
bed rest. In contrast, nerve root pain caused by an epidural tumor or abscess
begins more insidiously, and back pain is worsened by bed rest.

In patients with lumbosacral herniation,
straight-leg raises stretch the lower lumbar roots and exacerbate back or leg
pain (bilateral if disk herniation is central); straightening the knee while
sitting also causes pain.

Cauda equina compression often results in urine
retention or incontinence due to loss of sphincter function.

Diagnosis

MRI or
CT

MRI or CT can identify the cause and
precise level of the lesion. Rarely (ie, when MRI is contraindicated and CT is
inconclusive), CT myelography is necessary. Electrodiagnostic testing may help
identify the involved root. Because an asymptomatic herniated disk is common,
the clinician must carefully correlate symptoms with MRI abnormalities before
invasive procedures are considered.

Treatment

Conservative
treatment initially

Invasive
procedures if neurologic deficits are progressive or severe

Immediate
surgical evaluation if the spinal cord is compressed

Because a herniated disk desiccates and
shrinks over time, symptoms tend to abate regardless of treatment. Up to 85% of
patients with back pain—regardless of cause—recover without surgery within 6
wk.

Treatment should be conservative, unless
neurologic deficits are progressive or severe. Heavy or vigorous physical
activity is restricted, but ambulation and light activity (eg, lifting objects < 2.5
to 5 kg [≈ 5 to 10 lb] using correct techniques) are permitted as
tolerated; prolonged bed rest (including traction) is contraindicated. Acetaminophen, NSAIDs, or other
analgesics should be used as needed to relieve pain. If symptoms are not
relieved with nonopioid analgesics, corticosteroids can be given systemically
or as an epidural injection; however, analgesia tends to be modest and
temporary. Methylprednisolonemay be given, tapered
over a 6 days, starting with 24 mg po daily and decreased by 4 mg a day.

Physical therapy and home exercises can
improve posture and strengthen back muscles and thus reduce spinal movements
that further irritate or compress the nerve root.

Microscopic diskectomy and laminectomy
with surgical removal of herniated material are usually the procedures of
choice. Percutaneous approaches to remove bulging disk material are still being
evaluated. Dissolving herniated disk material with local injections of the
enzyme chymopapain is not recommended. Lesions acutely compressing the spinal
cord or cauda equina (eg, causing urine retention or incontinence) require
immediate surgical evaluation.

If cervical radiculopathies result in
signs of spinal cord compression, surgical decompression is needed immediately;
otherwise, it is done electively when nonsurgical treatments are ineffective.

Key Points

Herniated
disks are common and usually affect nerve roots at C6, C7, L5, or S1.

If
symptoms develop suddenly and back pain is relieved with rest, suspect a
herniated disk rather than an epidural tumor or abscess.

Recommend
analgesics, light activity as tolerated, and exercises to improve posture
and strength; however, if pain or deficits are severe or worsening,
consider invasive procedures.